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Competition and coevolution drive the evolution and the diversification of CRISPR immunity
Martin Guillemet1, Hélène Chabas1,2, Antoine Nicot1
1CEFE, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.
Nature Ecology & Evolution
|August 15, 2022
Summary
Host-pathogen coevolution, driven by competition, maintains bacterial CRISPR immunity diversity. New resistance mutations arise from fittest hosts, preventing extinctions and shaping evolving populations.
Area of Science:
- Evolutionary biology
- Microbial ecology
- Genetics
Background:
- Pathogen resistance diversity impacts host population dynamics.
- Host genotype competition and coevolution with pathogens shape resistance evolution.
- The evolutionary trajectory of host diversity under these pressures is not fully understood.
Purpose of the Study:
- To experimentally investigate how coevolving phage populations influence the diversification of bacterial CRISPR-Cas immunity.
- To elucidate the roles of negative-frequency-dependent selection and inter-host competition in maintaining resistance diversity.
- To understand the impact of fluctuating selective pressures on host-pathogen evolutionary dynamics.
Main Methods:
- Experimental evolution of bacterial and phage populations.
- Monitoring the diversification of CRISPR-Cas adaptive immune systems in bacteria.
- Analyzing the interplay between host competition and phage-driven selection.
Main Results:
- Coevolution with phages generates negative-frequency-dependent selection, maintaining bacterial resistance diversity.
- New resistance mutations are selected for in the host population.
- Asymmetries in competitive abilities among host genotypes drive host evolution.
- Fittest host genotypes acquire new CRISPR immunity to escape phage predation, preventing extinction.
- Fluctuating selection maintains diversity by introducing new resistance genotypes from initially fittest hosts.
Conclusions:
- Coevolutionary dynamics between hosts and pathogens are critical for maintaining resistance diversity.
- Competition among host genotypes significantly influences the transient dynamics of host-pathogen coevolution.
- CRISPR-Cas immunity diversification is a dynamic process shaped by fluctuating selective pressures and host competition.
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